Dwarf birch
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Dwarf birch ( Betula nana ) |
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The Betula nana ( Betula nana ), also polar birch called, is a species of the genus of birch ( Betula ) within the family of birch family (Betulaceae). It is distributed arctic-alpine in the northern hemisphere .
description
Vegetative characteristics
The dwarf birch grows as a deciduous, branched dwarf shrub , which in stormy, cold locations, in bush-like growth only grows from 0.2 meters (lying on the ground) to 0.5 meters, in sheltered locations usually as single or small groups Trees reach 0.5 to over 1.0 meters. It has lying or ascending branches. The black-gray bark of the branches is initially tomentose, later bald and dark red-brown in color.
The alternate arranged leaves are divided into short petioles and leaf blades. The almost circular leaf blade with a diameter of about 1 centimeter is glabrous, roughly notched. The upper side of the leaf is dark green and the underside is lighter and more nervous. After sprouting, the leaves are somewhat sticky, and in autumn they turn a strong golden yellow to intense carmine red.
In colder temperatures, the dwarf birch generally tends to vegetatively reproduce via breeding roots, whereas in warmer areas it tends to spread via seeds.
Generative characteristics
The flowering period extends from April to May. The dwarf birch is single-sexed ( monoecious ). The flowers are grouped in upright spherical to elongated catkins. The male kittens are 0.5 to 1.5 cm long with yellow stamens. The female kittens are light brown and 7 to 10 mm long.
After the fruits ripen into October, the seeds spread via wind and water.
The chromosome number for all three subspecies is 2n = 28.
ecology
The dwarf birch is a nanophanerophyte . The very slowly growing species can live up to 90 years, so that the annual rings of the maximally 40-46 mm wide trunks are only 0.23 mm wide on average. It has high lighting requirements and can therefore only compete poorly with other trees. The dwarf birch often grows with cranberries , cotton grass , sundew , rosemary heather or peat moss .
Occurrence
The dwarf birch is widespread in the northern hemisphere in the arctic-alpine region. In the arctic tundra their distribution area reaches up to about 80 degrees of latitude, the closed distribution area ranges from Scotland (mostly stock-forming there) and Scandinavia over Spitsbergen east to Siberia , west over Iceland and Greenland to Baffin Island in northern Canada . As a glacial relic , it has survived in isolated raised bogs in the temperate zone to the south. While the subspecies Betula nana subsp. nana is widespread on both sides of the Atlantic and eastward to central Siberia, Betula nana subsp. exilis to the Asian and North American regions from Western Siberia to Canada.
In Central Europe it grows sporadically in the North German lowlands, in the Harz , Bohemian Forest and Ore Mountains as well as in the Alpine foothills. In Austria it is also very rarely found in Lower Austria, Styria, Carinthia, Tyrol and Salzburg. It was extinct in Vorarlberg and Upper Austria, but was resettled from the Salzburg part of the Ibmer Moor .
When sites are waterlogged in Central Europe peat soils of high- and fens , but also bog meadows and edges of alder swamps preferred. It thrives on wet, nutrient-poor, base-poor, acidic peat soils. It often grows together with Vaccinium uliginosum in the Vaccinio uliginosi-Pinetum rotundatae from the Dicrano-Pinion association or in the Eriophoro-Trichophoretum cespitosi from the Sphagnion magellanici association.
Before the post-glacial reforestation of Central Europe, a broad belt of dwarf birch trees developed between the northern ice-edge location and the European high mountains, as in the tundra . Later this distribution area has in part areal split.
Danger
The dwarf birch is a "highly endangered" glacial relic in Germany . In the last few decades, several growing areas in Central Europe have become extinct. The dwarf birch could be seen as a "monument" of the post-glacial vegetation history. In Bavaria, as part of a study by the University of Regensburg, ten dwarf birch growth sites were identified, which probably include all Bavarian occurrences.
It is particularly endangered by drainage or, in general, by a lack of water in its habitat, as this leads to the growth of competitive woody plants and also of heather.
The dwarf birch is protected in Austria and Germany and is on the Red List of Endangered Species . In Austria, it is threatened with extinction in the western Alpine region and in the northern Alpine foothills . Depending on the hazard category, protective measures depending on the location (e.g. de-bushing, removal of dense stands of competing species, illumination) are recommended. In general, regular monitoring of existing relic populations is recommended, as significant changes can occur within 10 years. Refugia areas are now considered hotspots for genetic diversity. In terms of nature conservation, a genetic analysis of the Bavarian dwarf birch occurrences could therefore be important to investigate the relic status.
Common names
For the dwarf birch there are or existed, sometimes only regionally, the other German-language trivial names : Brockenbirke, Budern ( Zillertal ), Moorbirke ( Old High German ), Moosbirke, Morassbirke and Peat Birch.
literature
- Bruno P. Kremer: Shrub trees . Niedernhausen 2002, ISBN 3-576-11478-5 .
- Peter Schütt , Horst Weisgerber, Hans J. Schuck, Ulla Lang, Bernd Stimm, Andreas Roloff : Encyclopedia of Bushes. Nikol, Hamburg 2006, ISBN 3-937872-40-X , Betula nana pp. 19-24.
- BU Schwarz, P. Poschlod: The last of their kind in Bavaria - The Ice Age relic dwarf birch (Betula nana L.). A stock analysis with biological-ecological investigations. In: ANLiegen Natur. , 37, 1, Laufen, 2015, pp. 19–30. ( PDF 1.4 MB)
Individual evidence
- ↑ a b c d Erich Oberdorfer : Plant-sociological excursion flora for Germany and neighboring areas. 8th edition. Verlag Eugen Ulmer, Stuttgart 2001, ISBN 3-8001-3131-5 , p. 314.
- ↑ a b c d Burkhard Quinger: Dwarf Birch - Betula nana L. In: Information sheet on species protection 23rd Bavarian State Office for the Environment, 2009, accessed on August 12, 2019 .
- ↑ Betula nana at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
- ↑ a b BU Schwarz, P. Poschlod: The last of their kind in Bavaria - The Ice Age relict dwarf birch (Betula nana L.). A stock analysis with biological-ecological investigations. In: ANLiegen Natur. , 37, 1, 2015, pp. 19-30, Laufen.
- ^ Georg August Pritzel , Carl Jessen : The German folk names of plants. New contribution to the German linguistic treasure. Philipp Cohen, Hannover 1882, p. 59. (online)
Web links
- Dwarf birch. In: FloraWeb.de.
- Dwarf birch . In: BiolFlor, the database of biological-ecological characteristics of the flora of Germany.
- Betula nana L. In: Info Flora , the national data and information center for Swiss flora . Retrieved October 3, 2015.
- Distribution in the northern hemisphere according to Eric Hultén .
- Profile and distribution map for Bavaria . In: Botanical Information Hub of Bavaria .
- Thomas Meyer: Data sheet with identification key and photos at Flora-de: Flora von Deutschland (old name of the website: Flowers in Swabia ).
- John J. Furlow: Betulaceae. : Betula nana - the same text online as the printed work , In: Flora of North America Editorial Committee (Ed.): Flora of North America North of Mexico. Volume 3: Magnoliidae and Hamamelidae. Oxford University Press, New York and Oxford 1997, ISBN 0-19-511246-6 .
